This invention relates to a vehicle lamp, more particularly, to the construction of the reflective surface of its reflect component.
A typical modern type of vehicle lamps is shown in FIG. 7; the reflective surface 114a of the reflector 114 is composed of a plurality of diffusing reflector elements 114s and used in combination with a glass 116 having little or no refractive power to provide the light with a feeling of transparency or greater depth.
As is clear from FIG. 7, the plurality of diffusing reflector elements 114s are formed with reference to a single paraboloid of revolution P', so the increase in the diameter of the opening of the reflector 114 results in a corresponding increase in its depth dimension. If the vehicular structure and other design considerations limit the space for installing the identification lamp, the diameter of the opening of the reflector 114 has to be reduced but then the light emitting surface is reduced accordingly to make the lighting device look less attractive.
An improvement over this light is shown in FIG. 8; a reflective surface 214 is composed of a plurality of diffusing reflector elements 214s formed on a free curved surface Cf'. This increases the degree of freedom in the shape of the reflector 214 and even if only a limited space is available for installing the identification lamp, the reflective surface of the reflector 214 can be composed while ensuring a sufficient diameter for its opening.
However, the mere formation of diffusing reflector elements 214s on the free curved surface Cf to compose the reflective surface 214a causes the following problems. To assure the intended luminous intensity distribution from a vehicle lamp, diffusing light must be created in all directions from the optical axis Ax' of the reflector 214. If a plurality of diffusing reflector elements 214s are simply formed on the free curved surface Cf', the direction of the diffusing reflected light from each element varies randomly with the shape of the free curved surface Cf'; as a result, the directivity of the illuminating light from various parts of the reflective surface 214a cannot be sufficiently controlled to ensure the intended luminous intensity distribution for the lighting device. Further, depending on the position of individual diffusing reflector elements 214s on the free curved surface Cf', there will be no reflected light that travels from certain elements toward the optical axis Ax' and those elements are invisible if they are viewed right from the front of the lighting device being lit up. This makes the lighting device look less attractive.